This invention relates generally to a book clamp of a book binding machine and more particularly to a book clamp which is adapted to the demand of clamping books having a variation in thicknesses across their entire length.
In the technology of binding books such as booklets, magazines, periodicals and the like the use of clamps is well known where the clamps are utilized to clamp a book comprising a bundle of sheets or signatures being collated before in order to hold together the plurality of sheets or signatures for the succeeding working step of binding the sheets or signatures by applying glue to the spine. The sheets or signatures are held in a fixed manner so that they may be conveyed along the binding machine wherein a number of necessary working steps are performed in order to properly bind the complete book.
A clamp of this kind is known, for example, from U.S. Pat. No. 3,702,129. This document discloses a book binding machine having a plurality of book clamps being coupled and driven by an endless chain along a path. Each of the clamps has an outer clamp assembly which is pivotally mounted along a horizontally extending axis to an inner clamp assembly. These clamps, however, are not adaptable to slight variations of the thickness along the length of one book which may, for example, arise from inserts added to the book which do not have the same length as the sheets or the signatures of the book.
It is therefore an object of the present invention to provide a book clamp, especially a book clamp to be used in a book binding machine, where this clamp provides sufficient clamping force to the entire length of the clamped book portion even in the case of thickness variations of the clamped book portion.
According to a first aspect, the present invention is directed to a book clamp for a book binding machine having a first clamp member and a second clamp member the second clamp member being adapted to said first clamp member, the second clamp member comprising a first flexible spring plate being coupled to the second clamp member.
According to further aspect of the present invention the book clamp of the book binding machine has a first clamp member and a second clamp member being coupled to said first clamp member where the second clamp member comprises a first and a second flexible spring plate both being mounted on the second clamp member.
By mounting a flexible spring plate onto the second clamp member of the book clamp it is possible to adjust the clamping force to slight variations of the thickness across the book which primarily may be caused by inserts having a smaller size than the sheets or the signatures of the book. In addition, the shape of the spring plates allows for a two point contact normal to the spine length which enhances the frictional grip force significantly and, as a consequence, improves the pull force required at the leading corner to pull up the book of the clamp.
With the objects of the invention in view, there is also provided a book clamp for a book binding machine, the book clamp including a first clamp member, a second clamp member connected to the first clamp member, and a pressure plate connected to the second clamp member. The pressure plate has a flexible spring plate for pressing a book against the first clamp member and a second flexible spring plate for pressing a book against the first clamp member. The second flexible spring plate has an overlap portion and a portion of the first flexible spring plate overlaps the overlap portion.
In accordance with a concomitant feature of the invention, the flexible spring plate defines a concave surface facing the first clamp member and the second flexible spring plate has an overlap portion and a portion of the first flexible spring plate overlaps the overlap portion.